1. Field of the Invention
The present invention relates to an ophthalmic composition, particularly an ophthalmic composition having an excellent cleaning effect and in addition, an adequate safety for the eye, and specifically it relates to an ophthalmic solution such as eye drops and an agent for contact lenses such as a cleaning solution for contact lenses.
2. Discussion of Background
Conventionally, contact lenses have been classified into water-nonabsorptive contact lenses and water-absorptive contact lenses, and classified into hard contact lenses and soft contact lenses. On each of these contact lenses, a stain of e.g. lipids (eye lipids) derived from the tear may be deposited when the lens is put on the eye in some cases, and such a stain on the lens due to the tear may cause deterioration in comfortableness in wearing or eye problems such as failure of eyesight or congestion of cornea, and accordingly it is essential to apply a cleaning treatment to a contact lens in order to safely and comfortably use the contact lens every day.
For such a cleaning treatment of a contact lens, a proper cleaning solution for contact lenses having a cleaning or removing effect over a stain is usually used. As such a cleaning solution for contact lenses, various solutions having a surfactant as a cleaning component added and incorporated therein have been proposed, and one having a polyoxyalkylene block copolymer such as a polyoxyethylene-polyoxypropylene block copolymer or a derivative thereof incorporated may, for example, be known.
However, with respect to the cleaning solution containing a polyoxyalkylene block copolymer or its derivative as a cleaning component, importance is usually attached to safety for the eye, and the concentration of the cleaning component in the solution is suppressed to be as low as possible so that the standards for contact lenses such as diameter or base curve will not change and the shape or physical properties of the contact lenses will not be impaired. At such a low concentration of the cleaning component, no adequate cleaning power such as lipid-solubilizing power may be obtained. Accordingly, there is a fear that when a cleaning treatment of a contact lens is carried out by using such a cleaning solution, a stain of e.g. lipids tends to remain and be deposited on the contact lens, and the eye may harmfully be influenced.
On the other hand, JP-A-7-48595 proposes a solution for contact lenses containing, as an essential component to prevent inflammation of the eye, glycyrrhizic acid or its salt known as a therapeutic agent for e.g. inflammation or allergy from a long time ago, or glycyrrhetinic acid or its derivative, derived from glycyrrhizic acid. It has been clarified that glycyrrhizic acid or its salt has a structure comprising a hydrophobic triterpenoid compound and a hydrophilic glucuronic acid bonded by an ether linkage, and thus it has surface active properties, and accordingly a solution employing glycyrrhizic acid or its salt as a surfactant may have a cleaning effect over a stain.
Accordingly, the present inventors have conducted various studies on said glycyrrhizic acid and its salts and as a result, found that solutions having them alone incorporated therein have a low or no lipid-solubilizing power, and their cleaning effect over a stain of lipids is inadequate.
Under these circumstances, the present inventors have further conducted extensive studies and as a result, found that the above glycyrrhizic acid and its salts have an effect to significantly improve the lipid-solubilizing power which the above polyoxyalkylene block copolymer or its derivative possesses, and with a solution comprising at least one member selected from the group consisting of glycyrrhizic acid and its salts, together with at least one member selected from the group consisting of polyoxyalkylene block copolymers and their derivatives, both useful cleaning effect over a stain of lipids and reduction in toxicity against the eye can be achieved.
Accordingly, the present invention has been accomplished on the basis of the above discoveries, and it is an object of the present invention to provide an ophthalmic composition which is excellent in a cleaning effect over a stain in the eye or a stain on a contact lens, particularly a stain of lipids, and with which safety for the eye can adequately be secured.
According to the present invention, there is provided an ophthalmic composition which contains a component A consisting of at least one member selected from the group consisting of polyoxyalkylene block copolymers and their derivatives, and a component B consisting of at least one member selected from the group consisting of glycyrrhizic acid and its salts.